\smsubsection{Incomplete Audit Data}
When a machine
appears in the event log with recorded votes cast on it during
election day, but does not appear in the ballot image file, this
indicates that some ballots are missing from the ballot image
database. Incomplete DRE ballot images will prevent accurate manual
recount procedures. The reverse situation reveals the opposite
procedural error: the event log is not complete.  We developed a
technique that identifies incomplete databases.   

This analysis requires an event log and a ballot image file, where
both files record machine serial numbers for any events and ballots
cast.  Our analysis crosschecks these files for inconsistencies that
may reveal problems.  In our algorithm, we create two data structures;
the first contains every machine used for voting and how many votes
were cast on it according to the event log, the second contains every
machine with ballot images on it and how many ballots were cast on it
according to the ballot image file.  Then, we compare these two
structures.  Ideally, they would have the same contents and we could
conclude that the files are consistent.  However, if this is not the case, we
report file 
inconsistencies and provide the user with the machine serial number
and the conflicting vote counts.      
